Two Thrips for Possible Biological Control of Brazilian Peppertree

The invasive Brazilian peppertree has supplanted critical habitat for many organisms. In Florida, the peppertree has infested nearly 700,000 acres and has been particularly abundant in the Everglades. In general, the trees take over space where native plants should be. Animals such as white-tailed deer, the Florida panther, and migratory birds that depend on native vegetation for food and shelter are deprived of that habitat.

“This can have cascading effects through the food chain,” said Bill Overholt, an entomology professor at the University of Florida’s Indian River Research and Education Center in Fort Pierce.

Although scientists have not come up with a specific cost for Brazilian peppertree eradication efforts, the South Florida Water Management District estimates it spends $1.7 million per year to control the invasive tree. Herbicides are sometimes used to kill Brazilian peppertree, but researchers are looking for environmentally friendlier biological agents to permanently suppress growth and reproduction of the tree.

Recently, University of Florida and USDA researchers brought two populations of thrips (Pseudophilothrips ichini Hood) — tiny insects that often feed on plants — from Brazil to Florida laboratories, where they were tested for temperature requirements, reproductive ability, and their plant impact. The UF and USDA research was recently published in the the journal Biocontrol Science and Technology.

Both thrips feed on the Brazilian peppertree, but scientists found that one from Ouro Preto was more cold-tolerant than a thrips from farther north in Brazil. They predict the insect will thrive in Florida, where temperatures sometimes dip below freezing, which is only slightly colder than the insect is used to.

“The idea of biological control is to reunite these highly specialized natural enemies with their host plant, in this case Brazilian peppertree, to help reduce plant densities in the invaded area,” said Veronica Manrique, a UF senior biological scientist and lead author of the study. “We are also working with two other natural enemies, a psyllid and a defoliating weevil, which should further reduce Brazilian peppertree growth and reproduction in Florida.”

The scientists will now seek permission to release the thrips into areas where the Brazilian peppertree is growing. The USDA Animal and Plant Health Inspection Service will review the joint UF/IFAS and USDA petition for the thrips’ release, Overholt said. That agency typically takes 1.5 to two years to decide whether an insect is safe to use as a biological control agent.

“If we get this far, we will release the thrips at several locations in south and central Florida, initially mostly on public lands, because that’s where the problem is biggest,” Overholt said. “If we have success here, I’m sure folks in Hawaii and Texas will want to introduce the insect. Eventually, there may also be interest in other areas of the world, such as Australia.”